The invention relates to a device for processing a material web including an ultrasonic unit having a converter, a booster and a sonotrode, and a counter tool, wherein the material web is guided through a gap between the sonotrode and the counter tool and is acted upon by the sonotrode, wherein the ultrasonic unit is adjustable via a movable carriage in relation to the counter tool and the booster is firmly connected to the carriage.
It is known to use ultrasonic sonotrodes in order to connect, cut, perforate, punch, stamp, heat treat, or treat in a similar way material webs. In the case of sonotrodes, it is critical that their tip is pressed or pushed onto the material web with an exactly predefined force so that the energy required for the procedure can be introduced into the material web. Because of the heat generated during the procedure, the length of the operating tool, for example a sonotrode, changes and can lead to a change in the gap height. A gap that is too narrow usually leads however to deterioration in processing the material and may at times result in damage to the material web or the tools, because the contact pressure is excessive and thus excessive energy is introduced into the material web. A gap that is too wide results in an unacceptable welding or cutting quality because the contact pressure is inadequate. It is therefore sought to maintain the contact pressure at a desired value as constant as possible.
A change in the operating speed, i.e. the throughput rate of the material web through the working gap necessitates a change of the contact pressure, because for example at an increase in speed, the required welding energy has to be introduced into the material web within a shorter time. In this case, the contact pressure therefore has to be increased.
EP 0 790 888 A1 relates to a device for machining a material web having the configuration as mentioned above. This device is intended to maintain a gap for machining the material web as constant as possible so that the reaction forces are completely supported by the rigid bearing when the material thickness differs during operation. Thus, the sonotrode does not yield. A disadvantage of this device is that different welding forces are introduced into the material to be welded when the material thickness varies while the gap height is constant, causing different welding qualities. Moreover, supporting the sonotrode in the oscillation node cannot always be realized in a simple manner.